This description relates to non-invasive optical architectures of sensors for quantitative and sensitive detection of low concentration of species of interest in complex matrices that have significant specular and diffuse reflection and interfering signatures in the measured spectral regions. These sensors have to be invariant to changes in the background signals, changes in temperature and relative humidity, separation between the measured sample and the sensor surface, contact pressure at sensor-sample interface and other variable factors. In addition, the sensors should have small volume, low power requirements, be insensitive to mechanical disturbances and easy to use in mobile applications.
One example of the application of this technology is non-invasive detection of glucose by measurements through the skin in dermis and subcutaneous layer. Another example of the application of this device is monitoring of quantitative level of infection and/or healing in subsurface regions of the body in order to make decisions about non-invasive or invasive treatments. Yet another example is detection of subsurface contaminants in food items before buying them or consuming them.